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Implementation of neutralizing fields for particle–particle simulations using like charges

Published online by Cambridge University Press:  07 July 2021

Yinjian Zhao
Affiliation:
University of Southern California, Los Angeles, CA90007, USA Lawrence Berkeley National Laboratory, Berkeley, CA94720, USA
Chen Cui
Affiliation:
University of Southern California, Los Angeles, CA90007, USA
Yanan Zhang
Affiliation:
Arizona State University, Tempe, AZ85281, USA
Yuan Hu*
Affiliation:
State Key Laboratory of High Temperature Gas Dynamics, Institute of Mechanics, Chinese Academy of Sciences, Beijing100190, PR China
*
Email address for correspondence: [email protected]

Abstract

The particle–particle (PP) model has a growing number of applications in plasma simulations, because of its high accuracy of solving Coulomb collisions. One of the main issues restricting the practical use of the PP model is its large computational cost, which is now becoming acceptable thanks to state-of-art parallel computing techniques. Another issue is the singularity that occurs when two particles are too close. The most effective approach of avoiding the singularity would be to simulate particles with only like charges plus a neutralizing field, such that the short-range collisions are equivalent to those of using unlike charges. In this paper, we introduce a way of adding the neutralizing field by using the analytical solution of the electric field in the domain filled with uniformly distributed charges, for applications with homogeneous and quasi-neutral plasmas under a reflective boundary condition. Two most common Cartesian domain geometries, cubic and spherical, are considered. The model is verified by comparing simulation results with an analytical solution of an electron–ion temperature relaxation problem, and a corresponding simulation using unlike charges. In addition, it is found that a PP simulation using like charges can achieve a significant speed-up of 100 compared with a corresponding simulation using unlike charges, due to the capability of using larger time steps while maintaining the same energy conservation.

Type
Research Article
Copyright
Copyright © The Author(s), 2021. Published by Cambridge University Press

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